Plastic bobbin and a method of manufacturing such a bobbin

ABSTRACT

A bobbin ( 1 ) of plastic has a cylinder ( 2 ) and, formed integrally therewith, circumferential end flanges ( 3 ) and is made of a U-shaped channel. Each end flange ( 3 ) consists of a plurality of spaced-apart, essentially radial flange elements ( 4 ) which are distributed along the circumference of the cylinder ( 2 ). In a method of manufacturing such a bobbin, a U-shaped channel is made by injection moulding. The U shaped channel is given such a shape that its side walls consist of a plurality of spaced-apart wall elements which are distributed along the length of the channel. The channel is bent to form the cylinder ( 2 ) and its ends are connected with each other in this bent position.

FIELD OF THE INVENTION

The present invention relates to a bobbin of plastic, which has acylinder and, formed integrally therewith, circumferential end flangesand is made of a U-shaped channel, and a method of manufacturing such abobbin, in which method a U-shaped channel is made and bent to form saidcylinder with end flanges, the ends of the channel being connected witheach other in this bent position.

BACKGROUND ART

Bobbins are used for winding, inter alia, cable, and they can bemanufactured in various ways and of various materials. In small sizes,up to about 400 mm, they are in most cases made of plastic or paper.They can be manufactured in one piece or several pieces which are thenassembled.

GB-1,303,063 discloses manufacture of a bobbin by bending a plasticchannel back on itself so that its ends meet and a cylinder withcircumferential end flanges is formed, after which the ends are joinedby welding or gluing. The plastic channel is made by extrusion orthermoforming of a plastic strip and is provided with transversecorrugations to allow it to be bent to a cylinder.

The drawbacks of this method of manufacture is that it is time-consumingsince manufacture takes place in several steps and different machines ortools are required for each step, and that the corrugation requires agreat consumption of material.

SUMMARY OF THE INVENTION

The object of the invention is to provide a method that makes itpossible to simplify the manufacture of a bobbin of the above type andto reduce the consumption of material. A further object of the inventionis to provide such a bobbin which can be made of a smaller amount ofmaterial compared with the prior-art bobbin of a corresponding size andfurther has the advantage that it can be transported and stored in amore rational manner.

This object is achieved as regards the bobbin by a bobbin which is ofthe type mentioned by way of introduction and characterised in that eachend flange consists of a plurality of spaced-apart essentially radialflange elements which are distributed along the circumference of thecylinder.

For the end flanges of the bobbin to have sufficient strength, itsflange elements have over their entire radial extent preferably anessentially constant extension in the circumferential direction, theflange elements of each end flange having a total extension in thecircumferential direction which is essentially equal to thecircumference of the cylinder.

In order to facilitate bending, the bobbin has preferably a plurality ofaxial grooves which are formed in the outer circumferential surface ofthe cylinder, each groove extending the entire length of the cylinderbetween a point between two adjoining flange elements of one end flangeand a point between two adjoining flange elements of the other endflange.

Each flange element has at its radially inner end suitably a lug, whichextends past the inner circumferential surface of the cylinder and has acircumferential extent that decreases radially inwards. The U-shapedchannel can be bent until each lug has been brought into abutmentagainst a neighbouring lug. Thus the lugs make it easier to form theU-shaped channel to a cylinder which retains its cylindrical shape anddoes not collapse when used. In an alternative embodiment, the innercircumferential surface of the cylinder has a plurality of axialgrooves, each groove extending the entire length of the cylinder betweena point between two adjoining flange elements of one end flange and apoint between two adjoining flange elements of the other end flange. Thegrooves in the inner circumferential surface of the cylinder arepreferably located opposite to the grooves in the outer circumferentialsurface thereof and are preferably wedge-shaped in cross-section.

Preferably, at least one flange element of one end flange has at itsradially outer end an articulated projection which at its free end ishookable onto the other end flange.

The above object is achieved as regards the method by the U-shapedchannel being made by injection moulding and given such a shape that itsside walls consist of a plurality of spaced-apart wall elements whichare distributed along the length of the channel.

The ends of the channel are preferably connected with each other byprotrusions, which are formed on a projection of the base of thechannel, which projection projects at one channel end in thelongitudinal direction of the channel, being inserted into holes whichare formed in the base of the channel at the other channel end.

In order to facilitate bending of the channel, its base is duringinjection moulding given transverse inner grooves which extend theentire width of the base between a point between two adjoining wallelements of one channel wall and a point between two adjoining wallelements of the other channel wall.

Preferably, each wall element is during injection moulding at its endconnected with the base provided with a lug which extends past the baseand has an extent decreasing in the longitudinal direction of thechannel, away from the wall element, the channel being bent until eachlug is brought into abutment against a neighbouring lug, the lugsforming stops which make the channel form to a cylinder in connectionwith bending. Alternatively, the base of the channel can duringinjection moulding be given transverse outer grooves which extend theentire width of the base between a point between two adjoining wallelements of one channel wall and a point between two adjoining wallelements of the other channel wall.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail by means of apreferred but non-limiting embodiment and with reference to theaccompanying drawings.

FIG. 1 is a side view of a U-shaped channel which is used to manufacturea bobbin according to the invention.

FIG. 2 is a sectional view along line II-II in FIG. 1 and shows achannel segment of the channel.

FIG. 3A shows the channel segment in section along line IIIA-IIIA inFIG. 2.

FIG. 3 shows the channel segment in section along line IIIB-IIIB in FIG.2.

FIG. 4 is an end view of a bobbin which is made of a bent channelaccording to FIGS. 1 and 2.

FIG. 5 is a sectional view along line V-V in FIG. 4 and shows thebobbin.

DESCRIPTION OF PREFERRED EMBODIMENTS

The bobbin 1 according to the invention is made of plastic and has acylinder 2 with a circumferential end flange 3 at each cylinder end.Each end flange 3 consists of a plurality of spaced-apart radial flangeelements 4, which are perpendicular to the cylinder axis and uniformlydistributed along the circumference of the cylinder 2. In the preferredembodiment, all flange elements 4 have the same shape and size, but theycould just as well have different shapes and/or sizes. The flangeelements 4 have essentially the shape of an elongate rectangle, eachflange element being connected with the cylinder 2 at one short side ofthe rectangle. The total width of the flange elements 4 of each endflange 3 is approximately equal to the circumference of the cylinder 2.For increased strength, the flange elements 4 are internally providedwith radial stiffeners 14, or they are arched in cross-section.

Each flange element 4 of one end flange 3 is arranged opposite to aflange element 4 of the other end flange 3. Between the flange elements4 in each pair of adjoining flange elements, the cylinder 2 has axialgrooves 5 in its outer circumferential surface. The grooves 5 extend theentire length of the cylinder 2.

In an alternative embodiment (not shown), also the inner circumferentialsurface of the cylinder has axial grooves between the flange elements 4in each pair of adjoining flange elements, which grooves extend theentire length of the cylinder 2 and are wedge-shaped in cross-section.

Each cylinder portion 2′ between two adjoining grooves 5 is outwardlyarched in cross-section, as is evident from FIG. 3B, or inwardly archedin cross-section. To provide a more rigid cylinder, these portions 2′can be made more pointed in cross-section, as indicated by dashed linesin FIG. 3B.

Each flange element 4 has at its radially inner end a lug 6 whichextends past the inner circumferential surface of the cylinder 2 and hasa circumferential extent that tapers radially inwards (see FIGS. 1 and4). Each lug 6 tapers radially inwards in such a manner that, seen inthe axial direction, it has the shape of a radially outer part of asector of a circle, whose radius is equal to the inner radius of thecylinder 2 and whose point angle is 360°/N, where N equals the number offlange elements of each end flange 3.

One or more flange elements 4 of one end flange are at their radiallyouter end provided with an articulated projection 7, whose free end isto be hooked onto a hook 19 on a flange element 4 of the other endflange, so that the projection 7 forms a transport cover for a cablewound onto the bobbin.

The outer circumferential surface of the cylinder 2 has a hook 8 onwhich a cable end can be fastened when winding a cable onto the bobbin.

According to the invention, the bobbin 1 is manufactured by a U-shapedchannel 9 being injection moulded of plastic and then being bent back onitself to form a cylinder 2 with an end flange 3 at each cylinder end.The base 10 of the U-shaped channel 9 forms the cylinder 2 and its walls11 form the end flanges 3. To allow the channel 9 to be bent back onitself, its walls 11 consist of a plurality of essentially rectangularwall elements 12 which are spaced from each other and uniformlydistributed along the length of the channel 9. When the channel 9 isbent, the wall elements 12 are moved apart in the manner as is evidentfrom FIG. 4.

The channel ends 13 are connected with each other by protrusions 15,here having the shape of hooks, which are formed on a projection 17 ofthe base 10 of the channel, said projection projecting at one channelend 13 in the longitudinal direction of the channel 9, being insertedinto holes 16 which are formed in the base of the channel at the otherchannel end 13 (FIG. 2). Of course, it is also conceivable to form theholes in the projection 17 at one channel end 13 and the protrusions atthe other channel end 13.

The base projection 17 provided with the protrusions 15 at one channelend 13 also has an opening 18 through which the hook 8, which is formedat the other channel end 13, is inserted when interconnecting thechannel ends 13.

In an alternative embodiment (not shown), the channel ends are connectedwith each other by the projection at one channel end being insertedbetween two holder elements extended in the longitudinal direction ofthe channel and being essentially L shaped in cross-section, at thechannel end opposite to the projection. The first L legs of the twoholder elements are attached to the base. The two free second L legs areoriented towards each other and form supporting portions for theprojection when this is inserted between the holder elements wheninterconnecting the channel ends. A stop lug is arranged on the base ofthe channel between the two holder elements, the projection being formedwith a hole into which the stop lug is inserted once the channel endsare connected with each other. The holder elements are preferablyarranged on the outside of the base of the channel so that the completedbobbin obtains a smooth outer circumferential surface.

The base 10 of the channel 9 is formed with transverse inner grooves 5which make the channel easier to bend.

To facilitate the forming of a cylinder 2 when bending the U-shapedchannel 9, and to prevent the cylinder from collapsing when using thebobbin 1, each wall element 12 is provided with a lug 6 which extendspast the base 10 and has an extent decreasing in the longitudinaldirection of the channel 9, away from the wall element. The channel 9can be bent until each lug 6 is brought into abutment against aneighbouring lug 6. Alternatively, the base 10 of the channel is duringinjection moulding given transverse outer grooves which extend theentire width of the base between a point between two adjoining wallelements 12 of one channel wall 11 and a point between two adjoiningwall elements 12 of the other channel wall 11.

The bobbin according to the invention can be used not only for windingcable, but also for winding, for instance, rope, line, hose, emery clothand the like. The bobbin can also serve as a spacing or insulatingelement in large drums or pipes with cables inserted into the tube whichis formed of the cylinder of the bobbin.

1. A bobbin of plastic, which has a cylinder and, formed integrallytherewith, circumferential end flanges and is made of a U-shapedchannel, wherein the U-shaped channel is made by injection moulding inone piece, and that each end flange consists of a plurality ofspaced-apart, essentially radial flange elements which are distributedalong the circumference of the cylinder.
 2. A bobbin as claimed in claim1, in which the flange elements over the entire radial extent have anessentially constant extension in the circumferential direction, theflange elements of each end flange having a total extension in thecircumferential direction which is essentially equal to thecircumference of the cylinder.
 3. A bobbin as claimed in claim 1, inwhich a plurality of axial grooves are formed in the outercircumferential surface of the cylinder, each groove extending theentire length of the cylinder between a point between two adjoiningflange elements of one end flange and a point between two adjoiningflange elements of the other end flange.
 4. A bobbin as claimed in claim1, in which a plurality of axial grooves are formed in the innercircumferential surface of the cylinder, each groove extending theentire length of the cylinder between a point between two adjoiningflange elements of one end flange and a point between two adjoiningflange elements of the other end flange.
 5. A bobbin as claimed in claim3, in which the grooves in the inner circumferential surface of thecylinder are located opposite to the grooves in the outercircumferential surface thereof and are wedge-shaped in cross-section.6. A bobbin as claimed in claim 1, in which each flange element at itsradially inner end has a lug which extends past the innercircumferential surface of the cylinder and has a circumferential extentthat decreases radially inwards.
 7. A bobbin as claimed in claim 1, inwhich at least one flange element of one end flange at its radiallyouter end has an articulated projection which at its free end ishookable onto the other end flange.
 8. A method of manufacturing abobbin of plastic, which has a cylinder and, formed integrallytherewith, circumferential end flanges, in which method a U-shapedchannel is made in one piece and bent to form said cylinder with endflanges, the ends of the channel being connected with each other in thisbent position, wherein the U-shaped channel is made by injectionmoulding and given such a shape that its side walls consist of aplurality of spaced-apart wall elements which are distributed along thelength of the channel.
 9. A method as claimed in claim 8, in which thechannel ends are connected with each other by protrusions, which areformed on a projection of the base of the channel, which projectionprojects at one channel end in the longitudinal direction of thechannel, being inserted into holes which are formed in the base of thechannel at the other channel end.
 10. A method as claimed in claim 8, inwhich the base of the channel during injection moulding is giventransverse inner grooves which extend the entire width of the basebetween a point between two adjoining wall elements of one channel walland a point between two adjoining wall elements of the other channelwall.
 11. A method as claimed in claim 8, in which each wall elementduring injection moulding is at its end connected with the base providedwith a lug which extends past the base and has an extent decreasing inthe longitudinal direction of the channel, away from the wall element,and the channel is bent until each lug is brought into abutment againsta neighbouring lug.
 12. A method as claimed in claim 8, in which thebase of the channel during injection moulding is given transverse outergrooves which extend the entire width of the base between a pointbetween two adjoining wall elements of one channel wall and a pointbetween two adjoining wall elements of the other channel wall.